The "miracle" was achieved after a team of UC Berkeley mechanical engineers created a computerized body brace that the SF Chronicle compared to the Iron Man suit. Wearing the body brace, the 22-year old took his first steps -- in front of 15,000 cheering people -- since a 2007 car crash left his spinal cord severed above his hips.

The engineers call their contraption an "exoskeleton," and say that future models will help more wheelchair users like Whitney experience more freedom and mobility than ever thought possible.

Berkeley professor Homayoon Kazerooni and four doctoral students build the model Whitney used on Saturday, called E-Legs. It requires a power pack and also requires the user to walk with the assistance of crutches or a walker -- but the operative word is walk. Models like the one Whitney used are not yet widely available to the public, but Kazerooni's company hopes to sell similar models for $15,000 apiece, or roughly what a motorized wheelchair costs.

The exoskeleton works via a switch on the walker or crutches. The user operates the switch, telling the computer controlling the exoskeleton's movements where to go and what to do.